Which defense mechanism involves engulfing foreign particles?

Phagocytosis is a critical defense mechanism utilized by the immune system to protect the body from infection and disease. This process involves the engulfing of foreign particles, such as bacteria, viruses, and cellular debris, by specialized immune cells called phagocytes, which include macrophages and neutrophils. During phagocytosis, the phagocyte recognizes the foreign particle, surrounds it, and then consumes it, ultimately breaking it down within its internal cellular structures.

This process is vital for maintaining homeostasis in the body, eliminating pathogens, and clearing dead or damaged cells, thereby playing a crucial role in the body's overall immune response. The ability of phagocytes to detect, ingest, and destroy these unwanted entities is fundamental to both innate and adaptive immunity.